If you've never had a personal encounter with the norovirus, consider
yourself lucky. The virus, which causes severe diarrhea and vomiting in
human, is extremely contagious. It gained regained its notoriety in several
well-publicized cases of outbreaks
in cruise ships, and is estimated to have caused over 90% of epidemic
nonbacterial gastroenteritis in the world. Yet, scientists don't have
a very good understanding of the virus and how it works.

"Norovirus is one of the most infectious viruses of man,"
said Ian Goodfellow, a professor of virology at the department of pathology
at Britain's University of Cambridge, who has been studying noroviruses
for 10 years. [...]

What makes this such a formidable enemy is its ability to evade death
from cleaning and to survive long periods outside a human host. Scientists
have found norovirus can remain alive and well for 12 hours on hard
surfaces and up to 12 days on contaminated fabrics such as carpets and
upholstery. In still water, it can survive for months, maybe even years.

At the Health and Safety Laboratory in Derbyshire, northern England,
where researcher Catherine Makison developed the humanoid simulated
vomiting system and nicknamed him "Vomiting Larry", scientists
analyzing his reach found that small droplets of sick can spread over
three meters.

"The dramatic nature of the vomiting episodes produces a lot of
aerosolized vomit, much of which is invisible to the naked eye,"
Goodfellow told Reuters.

Larry's projections were easy to spot because he had been primed with
a "vomitus substitute", scientists explain, which included
a fluorescent marker to help distinguish even small splashes - but they
would not be at all easily visible under standard white hospital lighting.